BACTERIAL SPOT OF COWPEA AND LIMA BEAN 1 
By Max W. Gardner, Associate in Botany, and James B. Kendrick, Assistant 
in Botany , Purdue University Agricultural Experiment Station 2 
INTRODUCTION 
The bacterial spot disease of cowpeas was first noted in southern 
Indiana in 1919, but its bacterial nature was not determined until 
1921, when it occurred in an experimental plot of cowpeas at La Fay¬ 
ette, Ind. It is a typical spot disease of the leaves, stems, and pods, 
distinctly different from the other bacterial diseases of cowpeas 
reported in the literature. The organism which causes this disease 
also causes a very similar and widespread spot disease of lima beans 
which has been described recently by Tisdale and Williamson {23,24) , 3 
The work herein reported deals mainly with the symptoms of the 
disease as it occurs on cowpeas, the isolation, characteristics, over¬ 
wintering, pathogenicity, and dissemination of the causative bacteria, 
and the identity of the latter with the species causing the lima-bean 
disease. 
HISTORY AND OCCURRENCE 
A search of the literature has not revealed any previous description 
of this disease of cowpeas, although the symptoms of the spot disease 
of lima beans and cowpeas described by Smith {18, p. 15) in 1905, 
and attributed to Phyllosticta phaseolina Sacc., closely resemble those 
of the disease under consideration. A number of cases of bacterial 
infection of cowpeas have been recorded. Smith and McCulloch 
{19 ), in 1919, reported a wilt of cowpeas produced by inoculation with 
Bacterium solanacearum E. F. S. Smith {20, p. 280) mentions a bac¬ 
terial spot of cowpeas, but does not describe the disease. Rapd 
{15, p. 3) in 1920 and more recently Burkholder {3, p. 7) have reported 
infection of cowpeas with Bacterium phaseoli E. F. S., an organism 
which, however, differs radically in culture from the organism causing 
the spot disease. Wolf and Foster {25, p. 452) have isolated the 
tobacco wildfire organism {Bact. tabacum Wolf and Foster) from small, 
yellowish leaf spots on cowpeas grown near infected tobacco, but 
attribute the cowpea lesions to infection about leafhopper wounds. 
Osmun {14) has isolated the wildfire organism from lima beans 
grown adjacent to tobacco, and Johnson, Slagg, and Murwin {10, 
p . 177) successfully inoculated cowpeas with the, organism. How¬ 
ever, this organism differs culturally from the one causing the cowpea 
spot disease, and the writers’ attempts to inoculate tobacco have 
failed. The history of bacterial spot as it occurs on lima bean has 
been given by Tisdale and Williamson (24)- Chupp has reported 
to the Federal Plant Disease Survey the presence since 1918 of the 
disease on lima beans in New York. 
i Received for publication Nov. 11,1924; issued January. Contribution from the Department of Botany, 
Purdue University Agricultural Experiment Station, La Fayette, ’Ind. 
? The writers wish to acknowledge their indebtedness to Prof. H. S. Jackson for his advice and criticism. 
3 Reference is made by number (italic) to “Literature cited,” p. 862. 
Journal of Agricultural Research, 
Washington, D. C. 
( 841 ) 
Vol. XXXI, No 9. 
Nov. 1,1926. 
Key No. Ind.-15. 
